Reconstructed sailors' hammocks on the Kronan, a Swedish warship from the 1670's:
http://upload.wikimedia.org/wikipedia/commons/3/34/Kalmar_museum_Kronan_(shipp)_deck.JPG
Here you can see convicts' hammocks reproduced from early 19th century Australia.
http://melbourneblogger.blogspot.com/2010/07/francis-greenway-convict-architect-in.html
In the 19th century, at least, they seem to have become rather common for not only prisons and ships, but things like schools for wayward boys. They also became quite the rage as "lounging" became popular... at least among the wealthy who could afford to lounge. There are lots of mid 19th century paintings of lovely genteel ladies reposing comfortably in their hammocks among the springtime blossoms (while presumably, their servants and slaves were off working the fields and tending to the household...).
Michel Garnier, late 18th century?
http://18thcenturyblog.com/images/uploads/1269_original.png?1246630082
They were certainly known, at least to sailors and academics, and I have seen pictures of hammocks back to the 1500's, but I would suspect that the average 18th century man, particularly the backwoodsman, might never have seen nor heard of such a thing, and besides, even if he had, he was probably so used to sleeping on the ground or some other uncomfortable pallet that he wouldn't be able to stand the comfort of a hammock! :haha:
Making an 18th century hammock might be an interesting project.
I recently got a modern Hammock Bliss hammock with the mosquito net (and I have a tarp to go over it). I have stayed out in it only a few times, and yes, it can be somewhat difficult to get yourself and everything else arranged in the hammock (blankets and such), but once you do, let me tell you, it is WAY better than sleeping on the ground, a foam sleeping pad, an air mattress... or my bed in the house! Now, I'm a "side sleeper" and it is hard (but not impossible) for me to really lay on my side in the hammock, so I'm still getting used to it. And yes, you can lay more or less straight in it, by putting your feet to one side and your head to the other. :wink:
Of course, my modern nylon hammock rolls up into a ball and stuffs into its own sack to a space the size of a gallon jug, and doesn't weigh much at all. I can imagine that a linen or hemp 18th century hammock with all the heavy hemp ropes probably doesn't pack up nearly as small or light... :hmm: